1. Field of the Invention
The present invention relates generally to data synchronization, and, particularly, to material handling using queue time (Q-time) finite state confirmation to perform data synchronization.
2. Description of the Related Art
Manufacturing execution systems (MESs) assist production management staff in gathering field data and controlling field manufacturing procedures to provide enterprises with solutions for improved processes and productive benefit. MES is an information system integrating procedures of orders, suppliers, product management, production, equipment maintenance and quality control. Output data, either equipment settings or engineering data collection, from MES in wafer manufacturing is rather complex. In addition, data for synchronously updating production management systems or material management systems must typically be precise. It is important for MES to have an instantaneous and dependable data transmission environment.
Automated material handling systems (AMHS) transfer wafer lots between tools in wafer fabrication. Conventionally, material transfer in wafer fabrication is performed by wheel-based systems, increasing costs as wafer size increases from six inches to twelve inches. Furthermore, to optimize yield rate and purity, automated material handling has become standard in wafer fabrication.
MESs handle and locate lot positions of wafers based on messages from monitoring applications through the semiconductor equipment communication standard (SECS) protocol, especially for event-driven material handling systems (MHSs). Automated material handling must cooperate with MES real-time transfers. If transfer event reports from AMHS are lost or delayed, transport data from the MES will be inconsistent with real wafer process. However, delayed or missing messages are difficult to detect and recover in an event-driven MHS.
Furthermore, wafer lot movement is difficult to predict because of unbalanced loading and varied patterns of communication between host and tools, such that some critical transfer messages are delayed. Disconnection between the manufacturing execution and AMHSs can lose transfer messages such that the AMHS misses errors. Regular inventory of goods can solve this issue, but it is time consuming and less efficient. In addition, lost data may be caused by software bugs in the AMHS, creating additional costs to repair the program.
In view of this, what is called for is a system to reduce product search time and detect lost messages to enhance data consistency between manufacturing execution and AMHSs, and stabilize system software and hardware, thereby lowering manufacturing costs.